Unused screw holes in electric box cover plate

[snyderjp]

In our plant we have quad outlet boxes that have provisions to attach the cover plate with two screws. Most of the cover plates have four screw holes, so two are simply "left open". New personnel in safety have questioned this as unused penetrations in an electric box that need sealed per the NEC. I have always considered "penetrations" to refer to knockouts. I cannot find anything in the code that specifically addresses screw holes. Is there something I am missing?

 

[raider1]

Welcome to the forum.

This question was addressed in the 2008 NEC.

110.12 was revised to clarify that unused opening for mounting purposes are not required to be closed up.

Chris

 

[raider1]

Here is what the code says:

(A) Unused Openings. Unused openings, other than those
intended for the operation of equipment, those intended for
mounting purposes, or those permitted as part of the design
for listed equipment, shall be closed to afford protection substantially
equivalent to the wall of the equipment. Where metallic
plugs or plates are used with nonmetallic enclosures,
they shall be recessed at least 6 mm (1⁄4 in.) from the outer
surface of the enclosure.

Chris

 

[LarryFine]

JP, welcome to the forum!

If they insist, buy a bag of 6-32 or 8-32 nuts'n'bolts and fill 'em up.

 

[infinity]

As Chris stated this issue was dealt with a few code cycles ago. As ridiculous as it may seem there were inspectors that wanted the mounting holes in boxes sealed, hence the change.